The Final Week- Wrapping it Up

July 30th, 2012

Hey All,

So this is my final week out in Boise, and I have to say, it seems like just last week that I got into Boise! ~9 weeks later, it's about time to begin wrapping up my research out here. I've begun writing my AGu abstract, which I'm not too stressed about. Even though it's somewhat difficult to summarize 2 months of research into <200 words, I think I can handle it and will definitely get it in by the 8th of August.

This past week has been pretty busy for me. During this time I've gone through all of the passive seismic data recorded at Neal Hot Springs since last May, over 400 days of data. As I was working through the ample amounts of data, it seemed like on most days during a specific time interval, there was definitely characteristic fluid flow seismic waveforms that were being generated on the 10 seismic stations I am analyzing. Identifying the fluid flow events was the somewhat easy part (aside from deciding what is actually fluid flow and what is truck/man made noise). The difficult portion of looking through this data set, which took close to 5 days to analyze in depth, was trying to see if I can identify local events. It was like searching for a needle in a haystack, except there was no needle (so we think). Many of the events in the system were already catalogued through the NEIC database, but I was trying to find local events with frequencies greater than about 10 Hz, that were not catalogued in the event. Once I find these events, I can go in and look at P-wave arrival times relative to each seismic station so I can estimate the direction the waves are coming from. Unfortunately, only two very local events were found in the database, and these events appear to be arrving aprooximately 20-50 km outside of the Neal Hot Springs area, which suggests that these events were not caused by the fluid flow.

In a way this conclusion is great news for US Geothermal, in that their geothermal power plant is not creating any significant seismicity that could ultimately affect production. At first I looked at my finding and thought, "Wow all that time wasted, searching for something that does not exist!" However, after review and looking at the larger picture of this project, going forward if further monitoring of these stations shows that there is in fact an increased in seismicity located very close to the production zone of the hot springs, then it can be assumed that a recent event that the geothermal company began performing must have caused the seismicity.

Below you will see a map and a P-wave arrival screenshot. These waveforms come from a non-catalogued event that most likely originated to the northeast of Passive Seismic Station 4, not in the area of geothermal production.